Injection molding apparatus have been used to produce molded parts from thermoplastic resins such as polyolefins, polyvinyl chloride, polyesters, polycarbonates, and the like. With these thermoplastic resinous materials, typical injection molding temperatures employed are on the order of about 500.degree.-600.degree. F. and typical molding pressures are about 3,000 to 16,000 psi. While injection molding apparatus are used to successfully produce many types of plastic parts, they are not particularly suitable to produce relatively thin parts of less than about 0.50" as these thin parts typically require secondary finishing operations or are not acceptable as they contain blemishes or distortions due to non-uniform setting of the thermoplastics material.
Compression molding apparatus have also been used to produce molded parts from theromplastic resins, the molds employed generally being large and bulky as the parts produced therefrom are likewise generally large and bulky. With compression molding, lower pressures of about 1,000-3,000 psi can be used, but longer mold cycle times are needed to obtain thorough set of the resins. Thus, the molds employed must be strong enough to withstand these pressures and the elevated temperatures to accomodate the prolonged set periods. If relatively thin parts are to be produced such as those having cross sections less than about 1.0", they are generally not uniform or require secondary finishing operations.